Miniaturized Optical Pressure Sensor With Frustrated Total Internal Reflection
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Solution Overview
Problem
Existing optical pressure sensors are limited to measuring pressures on large surfaces and are not suitable for miniaturization.
Innovation Solution
An optical pressure sensor based on the principle of frustrated total internal reflection (FTIR) using an optical guide, elastically deformable elements, and photoresistors to detect pressure changes, allowing miniaturization and precise pressure measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If traditional optical pressure sensors are used, then pressure measurement capability is achieved, but device size remains large and cannot be miniaturized
Solution Approach 1:
The sensor is divided into distinct functional segments: an optical waveguide segment for light transmission, an elastically deformable element segment for pressure sensing, and a detector segment for signal detection. This segmentation allows each component to be optimized independently and facilitates miniaturization while maintaining measurement precision through specialized function allocation in each segment.
Solution Approach 2:
The elastically deformable element is nested within or integrated with the optical waveguide structure, and the detector is positioned to receive light from the waveguide. This nested arrangement allows multiple functional elements to occupy overlapping or adjacent spatial volumes, significantly reducing the overall sensor volume while maintaining all necessary pressure measurement functions.
2Volume of moving object
If the sensor is miniaturized, then device size is reduced, but sensitivity to pressure changes may be compromised
Solution Approach 1:
The elastically deformable element is designed with specific local mechanical properties (high elasticity and controlled stiffness) at the pressure contact region, while the optical waveguide maintains optimized optical properties locally. This local quality optimization ensures that even in a miniaturized sensor, the pressure-sensitive region exhibits high sensitivity to pressure changes while the overall device remains compact.
Solution Approach 2:
The sensor exploits changes in optical parameters (light intensity, reflection angle) that occur when the elastically deformable element deforms under pressure. By monitoring these parameter changes through the FTIR effect, the miniaturized sensor achieves high sensitivity comparable to or exceeding traditional larger sensors, as the optical parameter changes are amplified by the frustrated total internal reflection mechanism.
3Measurement precision
If FTIR-based measurement is implemented, then high measurement precision is achieved, but device complexity increases
Solution Approach 1:
The optical waveguide and pressure-sensing elastically deformable element are merged into a single integrated structure where the waveguide serves dual functions as both light transmission medium and pressure transmission path. This merging eliminates the need for separate mechanical linkages and reduces the number of optical components required, thereby simplifying the overall device while maintaining high measurement precision through the FTIR effect.
Solution Approach 2:
The optical waveguide performs multiple functions: it guides light from the source to the interaction region, transmits mechanical pressure from the elastically deformable element, and serves as one of the refractive interfaces for the FTIR effect. This multi-functionality reduces the total component count and simplifies the optical system architecture while preserving the high precision pressure measurement capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The sensor enables miniaturized pressure detection with high sensitivity and accuracy, capable of distinguishing between intentional and accidental hand actions, and providing real-time data without interfering with user experience.
Implementation Method 1
Total Internal Reflection (TIR) indicates the complete reflection of electromagnetic radiation within a material, in the presence of an interface with another material. The phenomenon occurs if the angle of incidence is greater than a certain limiting angle, called the critical angle
Implementation Method 2
in the presence of another material within this distance, with a refractive index at least equal to that of the first material, some of the radiation may propagate again and the reflection will not be complete. In this case we speak of frustrated total internal reflection
Implementation Method 3
at least one photoresistor configured to receive the output optical radiation and provide an electrical signal dependent on the pressure
Data Source
Figure 1~2
Figure 3~4
Figure 5~8
AI summary
An optical pressure sensor (100) is described comprising: an optical radiation source (1); an optical guide (2) optically coupled to the radiation source (2) and configured to obtain a total internal reflection condition; the optical guide (2) defining an interface wall (7) facing outward. The sensor further comprises: an element (3) elastically deformable and transparent to optical radiation having a face (8) facing said interface wall and such that, in the presence of a pressure exerted on said deformable element (3), it changes a contact area with the interface wall (7) so that the optical guide (2) assumes a frustrated total internal reflection condition with emission of an output optical radiation towards the first face (8) of the deformable element (3) dependent on the exerted pressure. The sensor further comprises a photoresistor (4) optically coupled to the second face of the deformable element (3) and configured to provide an electrical signal dependent on the output optical radiation.